Techniques for using multiple antennas have been used in cellular wireless communication systems as an effective means to improve robustness of data transmission and achieve higher data throughput. One of the multiple antenna techniques is space-time block coding (STBC). STBC is based on introducing joint correlations in transmitted signals in both the space and time domains to provide transmit diversity to combat fading channels.
The Alamouti scheme is the space-time block code to provide transmit diversity for systems with two transmit antennas. The Alamouti-based space-time block code has been widely used because of its simplicity and no need for the transmitter to know the channel state information (CSI) and therefore no need of channel feedback. Due to its effectiveness and easy implementation, the Alamouti-based space-time block code has been adopted into many wireless systems, such as WiMAX and WiFi. In third generation partnership project (3GPP), it was introduced in downlink transmissions in universal mobile telecommunication system (UMTS) since Release 99 and also adopted in downlink high speed downlink packet access (HSDPA) over higher speed data channels in Release 5. In the 3GPP standard, the implementation of Alamouti scheme is known as space time transmit diversity (STTD).
Enhanced uplink (EU), (also known as high speed uplink packet access (HSUPA)), is a feature that was introduced in 3GPP Release 6 to provide higher data rates in the uplink of UMTS wireless systems. The HSUPA may be configured to allow for much faster scheduling of uplink transmissions as well as lower overall data transmission latency.
Multiple antenna transmission/reception techniques with advanced signal processing are often referred to as multiple-input multiple-output (MIMO). MIMO has been widely studied and may significantly improve the performance of wireless communication systems.
Multiple antenna techniques have been widely adopted in many wireless communication systems such as IEEE 802.11n based wireless local area network access points and cellular systems like wideband code division multiple access (WCDMA)/high speed packet access (HSPA) and long term evolution (LTE). MIMO is introduced in WiMAX as well as in 3GPP. More advanced MIMO enhancements are currently being studied for 3GPP Release 9 and 10. Currently, only downlink (DL) MIMO is specified in 3GPP WCDMA standard.